In a hybrid vehicle having an automatic transmission (hereinafter called “AT”) combined with an electric-powered motor, when the hybrid vehicle is stopped and idling, an oil pump supplying an oil pressure to the AT stops pumping. As a result, the oil pressure needed for controlling the AT cannot be generated. To address this issue, the hybrid vehicle is equipped with a supplemental oil pump and supplemental electric-powered motor that drives the supplemental oil pump. Accordingly, the oil pressure which controls the AT can be generated not only when the car is running, but also when the car is idling. The addition of the supplemental oil pump and supplemental electric-powered motor may increase the overall cost and weight of the hybrid vehicle.